1. Field of the Invention
The present invention relates to a blower fan and, more particularly, to a blower fan providing reduced turbulence and increased amount of input and output air.
2. Description of Related Art
FIG. 1 illustrates a conventional blower fan comprising a housing 7, a stator 8 and an impeller 9. The housing 7 has an axial tube 71 mounted on a bottom of the housing 7, and an air inlet 72 and an air outlet 73 formed in a top and a side wall of the hosing 7 respectively. The stator 8 is coupled to the outer periphery of the axial tube 71. The impeller 9 has a shaft 91 rotatably coupled to the axial tube 71 through a bearing. The impeller 9 further includes a hub 92 and a plurality of vanes 93. The hub 92 has an upper cover 921 for the shaft 91 to couple with a center of the upper cover 921, a side wall 922 connecting with an outer periphery of the upper cover 921 and encircling the shaft 91, and an enclosing plate 923 connecting with a free end of the side wall 922 and radially extending outwards. The vanes 93 are formed on a surface of the enclosing plate 923, close to a radially outer edge of the surface, and spaced at a regular interval. Therefore, when the conventional blower fan starts working, air is drawn into the housing 7 by the impeller 9 via the air inlet 72 and then exit the housing 7 via the air outlet 73.
It should be noted that an upper edge of each vane 93 and the enclosing plate 923 are respectively parallel to a top and a bottom of the housing 7, with an air gap W between the upper edge of each vane 93 and the top of the housing 7 for avoiding friction or collision. However, during a period of time wherein the conventional blower fan works and the air is drawn into the housing 7 through the air inlet 72, an air pressure in the housing 7 forces the air to flow reversely toward the air inlet 72 through the air gap W. Accordingly, the amount of input air of the conventional blower fan is decreased adversely. Meanwhile, the air flowing reversely interfere with the air flowing in to the housing 7 and turbulence is easily produced. Accordingly, the overall noises of the conventional blower fan are increased, and the amount of output air is reduced. Hence, a novel blower fan is required to solve the problem.